The prior art discloses the extrusion of various
The prior art discloses the extrusion of various resins utilizing a variety of techniques. One area of resin extrusion, important in the industry of today, is concerned with the formation of polymeric sheet materials such as thermoplastic cellular material, which can be reshaped in thermoforming operations. A method common to the industry involves the use of polystyrene in the form of beads or pellets which is combined with a suitable nucleating agent and an expanding agent, and heated and cooled within fairly strict limits before entering the die of the extruding process. Prior art patents concerned with extruding thermoplastic cellular material which are related to the subject matter of this invention are U.S. Pat. Nos. 3,444,283 and 3,482,006.